CN110595604A - High dynamic range dual wavelength distributed optical fiber vibration demodulation system and method - Google Patents
High dynamic range dual wavelength distributed optical fiber vibration demodulation system and method Download PDFInfo
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Abstract
本发明公开了一种高动态范围的双波长分布式光纤振动解调系统，它包括第一窄带激光器、第二窄带激光器、密集波分复用器、脉冲光调制器、掺铒光纤放大器、光环形器、光纤光栅对阵列、三分三耦合器、第一法拉第旋转镜、第二法拉第旋转镜、第一密集波分解复用器、第二密集波分解复用器、第三密集波分解复用器和多通道数据采集卡，本发明基于分布式光纤光栅振动传感系统，采用双波长干涉和3×3耦合器数字相位解调技术，利用双波长回归分析相位解缠原理，从原理上克服了传统相位解缠中的π相位限制原则，从而实现了在分布式光纤振动传感系统中低采样率下精确跟踪实际强振动信号引起的相位大范围瞬时变化。
The invention discloses a high dynamic range dual-wavelength distributed optical fiber vibration demodulation system, which comprises a first narrowband laser, a second narrowband laser, a dense wavelength division multiplexer, a pulse light modulator, an erbium-doped fiber amplifier, an optical ring shaper, fiber grating pair array, three-thirds coupler, first Faraday Rotating Mirror, second Faraday Rotating Mirror, first DWDM, second DWDM, third DWDM The device and multi-channel data acquisition card, the invention is based on the distributed fiber grating vibration sensing system, adopts dual-wavelength interference and 3×3 coupler digital phase demodulation technology, and uses dual-wavelength regression to analyze the principle of phase unwrapping. It overcomes the π phase limitation principle in traditional phase unwrapping, thereby realizing the accurate tracking of large-scale instantaneous changes in phase caused by actual strong vibration signals at low sampling rates in distributed optical fiber vibration sensing systems.
Description
技术领域technical field
本发明涉及光纤传感技术领域，具体地指一种高动态范围的双波长分布式光纤振动解调系统及方法。The invention relates to the technical field of optical fiber sensing, in particular to a high dynamic range dual-wavelength distributed optical fiber vibration demodulation system and method.
背景技术Background technique
光纤传感技术自问世以来，就凭借诸多优势而被广泛关注并深入研究。光纤自身的电绝缘、本征安全、抗电磁干扰的特性使得其较传统的电类传感器在高温、高湿、强电磁干扰的恶劣环境中具有更优异的传感性能和更广阔的应用前景。光纤同时具有传感和传输的双重作用，且质量轻、线径细，利用各种复用技术可以大规模组网可以形成分布式传感网络。Since its inception, optical fiber sensing technology has been widely concerned and deeply researched due to its many advantages. The characteristics of electrical insulation, intrinsic safety and anti-electromagnetic interference of optical fiber make it have better sensing performance and broader application prospects than traditional electrical sensors in harsh environments with high temperature, high humidity and strong electromagnetic interference. Optical fiber has the dual functions of sensing and transmission at the same time, and is light in weight and thin in wire diameter. Various multiplexing technologies can be used to form a large-scale network and a distributed sensor network can be formed.
振动是自然界最普遍的现象之一，通过振动的检测可以实现结构健康监测、灾害和异常事件的预警等。振动检测是分布式光纤传感技术中的一个重要研究方向和应用领域，在分布式光纤振动传感技术中，分布式干涉型光纤光栅振动传感技术是其中的优秀代表之一。它利用低损耗分布式大容量全同弱光纤光栅阵列结合光学干涉，形成的干涉信号强度要比传统的后向瑞利散射高3～4个数量级，能够获得较高信噪比的振动解调信号，在基础设施和大型结构，如油气管道、油气储备基地、光缆、铁轨、边海防线以及重要设施周界安防等方面有着广阔的应用前景。Vibration is one of the most common phenomena in nature, and the detection of vibration can realize structural health monitoring, early warning of disasters and abnormal events, etc. Vibration detection is an important research direction and application field in distributed optical fiber sensing technology. In distributed optical fiber vibration sensing technology, distributed interference fiber grating vibration sensing technology is one of the outstanding representatives. It uses a low-loss distributed large-capacity isotactic weak fiber grating array combined with optical interference, and the interference signal intensity formed is 3 to 4 orders of magnitude higher than the traditional back Rayleigh scattering, which can obtain vibration demodulation with a higher signal-to-noise ratio. Signals have broad application prospects in infrastructure and large-scale structures, such as oil and gas pipelines, oil and gas storage bases, optical cables, railway tracks, border and sea defense lines, and perimeter security of important facilities.
目前，分布式干涉型光纤光栅振动传感器仍采用单波长干涉相位解调技术，它根据相位的连续性，通过比较相邻两点之间相位差来进行相位解缠。这种技术的局限性在于相邻两点的光程差变化不能超过波长值的一半，因此对于一定的动态测量范围需要足够高的采样率，这对数据采集系统的要求颇高，特别是在串有成千上万个光纤光栅传感器的长距离分布式光纤振动传感系统中，极大地增加了对相位解调系统的负荷。虽然已知有多种相位解缠的方法被提出，比如合成波长法(Gass J,Dakoff A,Kim M K.Phase imagingwithout 2π ambiguity by multiwavelength digital holography[J].Optics Letters,2003,28(13):1141-3.)和双波长法(张冰,王葵如,颜玢玢,et al.基于双波长和3×3光纤耦合器的干涉测量相位解卷绕方法[J].光学学报,2018,38(4):224-231.)，前者利用两种不同波长的激光获得两组干涉信号，求出相较于原双波长值更大的合成波长的相位信息，由于噪声正比于波长，由合成波长得到的相位噪声比较大。后者加以改进，利用合成波长的缠绕相位对单一波长的缠绕相位进行相位补偿，得到了较大范围、无差错的相位变化信息，也使得信噪比水平达到单波长的水平，但是其中合成波长的相位解缠依然受到传统π相位原则的限制。同时，分布式光纤光栅传感网络需要用到高功率掺铒光纤放大器，其主要工作在1.55μm波段，因此两种方法中的双波长都不适合于分布式光纤光栅振动传感，且分布式干涉型光纤光栅振动解调系统在铁轨、周界安防、光纤水听器等存在大幅度分布式振动信号测量需求的应用领域中仍面临很多困难和挑战。At present, the distributed interferometric fiber grating vibration sensor still adopts the single-wavelength interferometric phase demodulation technology, which performs phase unwrapping by comparing the phase difference between two adjacent points according to the continuity of the phase. The limitation of this technique is that the optical path difference of two adjacent points cannot change more than half of the wavelength value, so a sufficiently high sampling rate is required for a certain dynamic measurement range, which has high requirements on the data acquisition system, especially in In the long-distance distributed optical fiber vibration sensing system with thousands of fiber grating sensors in series, the load on the phase demodulation system is greatly increased. Although many methods of phase unwrapping have been proposed, such as the synthetic wavelength method (Gass J, Dakoff A, Kim M K. Phase imaging without 2π ambiguity by multiwavelength digital holography [J]. Optics Letters, 2003, 28(13) : 1141-3.) and the dual-wavelength method (Zhang Bing, Wang Kuiru, Yan Fingping, et al. Interferometric phase unwinding method based on dual-wavelength and 3×3 fiber couplers [J]. Acta Optics, 2018, 38(4):224-231.), the former uses two different wavelengths of laser light to obtain two sets of interference signals, and obtains the phase information of the synthesized wavelength that is larger than the original dual wavelength value. Since the noise is proportional to the wavelength, it is given by The phase noise obtained by the synthesized wavelength is relatively large. The latter is improved by using the winding phase of the synthesized wavelength to perform phase compensation on the winding phase of a single wavelength, and obtains phase change information with a wide range and no error, and also makes the signal-to-noise ratio reach the level of a single wavelength. The phase unwrapping of is still limited by the traditional π-phase principle. At the same time, the distributed fiber grating sensing network needs to use high-power erbium-doped fiber amplifiers, which mainly work in the 1.55 μm band, so the dual wavelengths in the two methods are not suitable for distributed fiber grating vibration sensing, and distributed The interferometric fiber grating vibration demodulation system still faces many difficulties and challenges in the application fields that require large-scale distributed vibration signal measurement, such as railway tracks, perimeter security, and fiber optic hydrophones.
发明内容SUMMARY OF THE INVENTION
本发明的目的就是要提供一种高动态范围的双波长分布式光纤振动解调系统及方法。本发明基于分布式光纤光栅振动传感系统，采用双波长干涉和3×3耦合器数字相位解调技术，利用双波长回归分析相位解缠原理，从原理上克服了传统相位解缠中的π相位限制原则，从而实现了在分布式光纤振动传感系统中低采样率下精确跟踪实际强振动信号引起的相位大范围瞬时变化，同时具有良好的和单波长干涉测量一致的信噪比水平。The purpose of the present invention is to provide a high dynamic range dual-wavelength distributed optical fiber vibration demodulation system and method. The invention is based on a distributed fiber grating vibration sensing system, adopts dual-wavelength interference and 3×3 coupler digital phase demodulation technology, and uses dual-wavelength regression to analyze the principle of phase unwrapping, which overcomes the π in traditional phase unwrapping in principle. The principle of phase limitation is adopted, so that the large-scale instantaneous phase change caused by the actual strong vibration signal can be accurately tracked at a low sampling rate in the distributed optical fiber vibration sensing system, and at the same time, it has a good signal-to-noise ratio consistent with single-wavelength interferometry.
为实现此目的，本发明所设计的一种高动态范围的双波长分布式光纤振动解调系统，其特征在于：它包括第一窄带激光器、第二窄带激光器、密集波分复用器、脉冲光调制器、掺铒光纤放大器、光环形器、光纤光栅对阵列、三分三耦合器、第一法拉第旋转镜、第二法拉第旋转镜、第一密集波分解复用器、第二密集波分解复用器、第三密集波分解复用器和多通道数据采集卡，其中，第一窄带激光器和第二窄带激光器用于分别向密集波分复用器输送波长为λ1和λ2的两路窄线宽激光信号，密集波分复用器的双波长连续光输出端连接脉冲光调制器的信号输入端，脉冲光调制器的双波长窄光脉冲输出端连接掺铒光纤放大器的输入端，掺铒光纤放大器的输出端连接光环形器的第一端口，光环形器的第二端口接入光纤光栅对阵列、光环形器的第三端口连接三分三耦合器的左侧第一通信端、光环形器的第四端口连接第一密集波分解复用器的输入端，三分三耦合器的左侧第二通信端连接第二密集波分解复用器的输入端、三分三耦合器的左侧第三通信端连接第三密集波分解复用器的输入端、三分三耦合器的右侧第一通信端通过延时光纤连接第一法拉第旋转镜、三分三耦合器的右侧第二通信端悬空、三分三耦合器的右侧第三通信端连接第二法拉第旋转镜，第一密集波分解复用器、第二密集波分解复用器和第三密集波分解复用器的输出端分别通过多通道光电探测器连接多通道数据采集卡的输入端。In order to achieve this purpose, a high dynamic range dual-wavelength distributed optical fiber vibration demodulation system designed by the present invention is characterized in that: it includes a first narrowband laser, a second narrowband laser, a dense wavelength division multiplexer, a pulse Optical modulator, erbium-doped fiber amplifier, optical circulator, fiber grating pair array, three-point three-coupler, first Faraday rotating mirror, second Faraday rotating mirror, first dense wave decomposition multiplexer, second dense wave decomposition The multiplexer, the third dense wave decomposition multiplexer and the multi-channel data acquisition card, wherein the first narrowband laser and the second narrowband laser are used to respectively deliver two narrowband wavelengths of λ1 and λ2 to the dense wavelength division multiplexer. For the linewidth laser signal, the dual-wavelength continuous light output end of the dense wavelength division multiplexer is connected to the signal input end of the pulsed light modulator, and the dual-wavelength narrow light pulse output end of the pulsed light modulator is connected to the input end of the erbium-doped fiber amplifier. The output end of the erbium fiber amplifier is connected to the first port of the optical circulator, the second port of the optical circulator is connected to the fiber grating pair array, and the third port of the optical circulator is connected to the left first communication end of the three-point three-coupler, The fourth port of the optical circulator is connected to the input end of the first dense wave demultiplexer, and the second communication end on the left side of the three-to-three coupler is connected to the input end of the second dense wave demultiplexer and the three-to-three coupler. The third communication end on the left side is connected to the input end of the third dense wave demultiplexer, the first communication end on the right side of the three-point three-coupler is connected to the first Faraday rotating mirror through a delay fiber, and the right side of the three-point three-coupler is connected. The second communication terminal on the side is suspended, the third communication terminal on the right side of the three-to-three coupler is connected to the second Faraday rotating mirror, the first dense wave demultiplexer, the second dense wave demultiplexer and the third dense wave demultiplexer. The output end of the device is respectively connected to the input end of the multi-channel data acquisition card through the multi-channel photodetector.
一种根据上述解调系统的高动态范围的双波长分布式光纤振动解调方法，它包括如下步骤：A dual-wavelength distributed optical fiber vibration demodulation method according to the high dynamic range of the above-mentioned demodulation system, which comprises the following steps:
步骤1：第一窄带激光器和第二窄带激光器分别向密集波分复用器输送波长为λ1和λ2的两路窄线宽激光信号，密集波分复用器将波长为λ1和λ2的两路激光信号进行波分复用，输出双波长光信号；Step 1: The first narrowband laser and the second narrowband laser transmit two narrow linewidth laser signals with wavelengths λ 1 and λ 2 to the DWDM respectively, and the DWDM converts the wavelengths λ 1 and λ The two laser signals of 2 are wavelength-division multiplexed to output dual-wavelength optical signals;
步骤2：脉冲光调制器利用双通道脉冲程序发生器通道一产生的电脉冲，将双波长连续光调制为双波长窄光脉冲，随后进入掺铒光纤放大器后，输出放大了峰值功率的窄脉冲光信号；Step 2: The pulse light modulator modulates the two-wavelength continuous light into two-wavelength narrow light pulses by using the electrical pulses generated by the two-channel pulse program generator channel 1, and then enters the erbium-doped fiber amplifier to output narrow pulses with amplified peak power. light signal;
步骤3：放大了峰值功率的窄脉冲光信号从光环形器的第一端口接入，从光环形器的第二端口输出到光纤光栅对阵列(8)中，光纤光栅对阵列中的每个光纤光栅对形成一个反射面，用于反射双波长光脉冲，在光纤光栅对阵列中，前一个光纤光栅对反射的双波长窄光脉冲与后一个光纤光栅对反射的双波长窄光脉冲在时间上刚好重合，从而在由三分三耦合器、第一法拉第旋转镜、第二法拉第旋转镜和延时光纤构成的非平衡迈克尔逊干涉仪中形成双波长干涉信号，并且两个波长的激光之间各自进行干涉、互不影响，三分三耦合器再将双波长干涉光进行分光处理，输出具有预设相位差的三路干涉光；Step 3: The narrow pulse optical signal with amplified peak power is connected from the first port of the optical circulator, and output from the second port of the optical circulator to the fiber grating pair array (8), each of the fiber grating pair arrays. The fiber grating pair forms a reflective surface for reflecting dual-wavelength light pulses. In the fiber grating pair array, the dual-wavelength narrow light pulses reflected by the former fiber grating pair and the dual-wavelength narrow light pulses reflected by the latter fiber grating pair are in time. The two wavelengths coincide with each other, so that a two-wavelength interference signal is formed in an unbalanced Michelson interferometer composed of a three-point three-coupler, a first Faraday rotating mirror, a second Faraday rotating mirror, and a time-delay fiber, and the two wavelengths of laser light The two-wavelength interference light is separated and processed by the three-point three-coupler, and the three-way interference light with preset phase difference is output;
步骤4：所述第一密集波分解复用器用于对三分三耦合器输出的第一路干涉光进行波分解复用得到第一组波长为λ1和λ2的两路干涉光，第二密集波分解复用器用于对三分三耦合器输出的第二路干涉光进行波分解复用得到第二组波长为λ1和λ2的两路干涉光，第三密集波分解复用器用于对三分三耦合器输出的第三路干涉光进行波分解复用得到第三组波长为λ1和λ2的两路干涉光，三组波长为λ1和λ2的两路干涉光分别在多通道光电探测器中进行光电转换后输送到多通道数据采集卡中；Step 4: The first dense wave demultiplexer is used to demultiplex the first channel of interference light output by the three-point three-coupler to obtain a first group of two channels of interference light with wavelengths λ 1 and λ 2 . The two-dense wave demultiplexer is used to demultiplex the second channel of interference light output by the three-point three-coupler to obtain a second group of two channels of interference light with wavelengths of λ 1 and λ 2 , and the third DW demultiplexer The device is used to demultiplex the third interference light output by the three-point three-coupler to obtain a third group of two interference lights with wavelengths λ 1 and λ 2 , and three groups of two interference lights with wavelengths λ 1 and λ 2 . The light is respectively photoelectrically converted in the multi-channel photodetector and then sent to the multi-channel data acquisition card;
步骤5：所述多通道数据采集卡利用三分三耦合器数字解调算法和双波长回归分析算法对接收到的三组波长为λ1和λ2的两路干涉光强电信号进行相位解调和解缠，得到对应的分布式振动信息。Step 5: The multi-channel data acquisition card uses a three-point three-coupler digital demodulation algorithm and a dual-wavelength regression analysis algorithm to perform a phase solution on the three groups of received two-way interference light intensity electrical signals with wavelengths λ 1 and λ 2 . Reconcile and disentangle to obtain the corresponding distributed vibration information.
与现有技术相比，本发明具有如下显著效果：Compared with the prior art, the present invention has the following remarkable effects:
1、本发明采用声光调制器作为脉冲光调制器，将双波长激光调制为具有低插损、高消光比、高稳定性的双波长窄光脉冲，为双波长分布式光纤振动解调系统提供了稳定可靠的双波长窄光脉冲激光光源；1. The present invention adopts an acousto-optic modulator as a pulsed light modulator to modulate a dual-wavelength laser into a dual-wavelength narrow light pulse with low insertion loss, high extinction ratio and high stability, which is a dual-wavelength distributed optical fiber vibration demodulation system. Provides a stable and reliable dual-wavelength narrow pulse laser light source;
2、本发明采用现代数字化相位解调技术，较传统的硬件解调技术而言，此方法具有结构更加简单，运算量更小，动态范围更大等优点。同时，考虑到3×3耦合器在双波长下的非完全对称性、光源输出功率不稳定、光电探测器工作效率不一致、光路中元件耦合损失等因素造成的3×3耦合器相位解调精度，本发明采用基于最小二乘的李萨如椭圆拟合方法实现3×3耦合器在双波长下的输出相位特性参数估计，3×3耦合器的耦合输出相位差精度控制在0.2°以内；2. The present invention adopts modern digital phase demodulation technology. Compared with the traditional hardware demodulation technology, this method has the advantages of simpler structure, smaller calculation amount and larger dynamic range. At the same time, the phase demodulation accuracy of the 3×3 coupler caused by the non-complete symmetry of the 3×3 coupler at two wavelengths, the unstable output power of the light source, the inconsistent working efficiency of the photodetector, and the coupling loss of the components in the optical path are considered. , the present invention adopts the Lissajous ellipse fitting method based on the least squares to realize the estimation of the output phase characteristic parameters of the 3×3 coupler under two wavelengths, and the coupling output phase difference accuracy of the 3×3 coupler is controlled within 0.2°;
3、本发明利用了双波长回归分析相位解缠原理，较传统的单波长或者合成波长解调技术而言，此方法具有更大的测量范围，同时降低了对数据采集系统采样率的要求。3. The present invention utilizes the dual-wavelength regression analysis phase unwrapping principle. Compared with the traditional single-wavelength or synthetic wavelength demodulation technology, this method has a larger measurement range and reduces the requirement for the sampling rate of the data acquisition system.
4、本发明利用弱光纤光栅对阵列进行双波长分布式光纤振动解调，可以实现长距离的高动态范围的振动探测，因此，可以将本发明所述振动解调系统更好地适用于铁轨、周界安防、光纤水听器等存在大幅度分布式振动信号测量需求的应用领域。4. The present invention utilizes the weak fiber grating to perform dual-wavelength distributed optical fiber vibration demodulation on the array, which can realize long-distance and high dynamic range vibration detection. Therefore, the vibration demodulation system of the present invention can be better applied to railway tracks. , perimeter security, fiber optic hydrophones and other application fields that have large-scale distributed vibration signal measurement requirements.
附图说明Description of drawings
图1为本发明的结构示意图；Fig. 1 is the structural representation of the present invention;
其中，1—第一窄带激光器、2—第二窄带激光器、3—密集波分复用器、4—脉冲光调制器、5—双通道脉冲程序发生器、6—掺铒光纤放大器、7—光环形器、8—光纤光栅对阵列、9—光纤光栅对、10—布拉格波长为λ1的光纤光栅、11—布拉格波长为λ2的光纤光栅、12—传感光纤、13—三分三耦合器、14—延时光纤、15—第一法拉第旋转镜、16—第二法拉第旋转镜、17—第一密集波分解复用器、18—第二密集波分解复用器、19—第三密集波分解复用器、20—多通道光电探测器、21—多通道数据采集卡。Among them, 1—first narrowband laser, 2—second narrowband laser, 3—dense wavelength division multiplexer, 4—pulse optical modulator, 5—dual-channel pulse program generator, 6—erbium-doped fiber amplifier, 7— Optical circulator, 8—fiber grating pair array, 9—fiber grating pair, 10—fiber grating with Bragg wavelength of λ 1 , 11—fiber grating with Bragg wavelength of λ 2 , 12—sensing fiber, 13—three-thirds Coupler, 14—delay fiber, 15—first Faraday rotating mirror, 16—second Faraday rotating mirror, 17—first dense wave demultiplexer, 18—second dense wave demultiplexer, 19—first Three dense wave decomposition multiplexers, 20-multi-channel photodetector, 21-multi-channel data acquisition card.
具体实施方式Detailed ways
以下结合附图和具体实施例对本发明作进一步的详细说明：The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments:
如图1所示的高动态范围的双波长分布式光纤振动解调系统，它包括第一窄带激光器1、第二窄带激光器2、密集波分复用器3、脉冲光调制器4、掺铒光纤放大器6、光环形器7、光纤光栅对阵列8、三分三耦合器13(3×3耦合器，从左边任意端口进，右边三路都可以出)、第一法拉第旋转镜15、第二法拉第旋转镜16、第一密集波分解复用器17、第二密集波分解复用器18、第三密集波分解复用器19和多通道数据采集卡21，其中，第一窄带激光器1和第二窄带激光器2的激光信号输出端用于分别向密集波分复用器3的两个激光信号输入端输送波长为λ1和λ2的两路窄线宽激光信号，密集波分复用器3的双波长连续光输出端连接脉冲光调制器4的信号输入端，脉冲光调制器4的双波长窄光脉冲输出端连接掺铒光纤放大器6的输入端，掺铒光纤放大器6的输出端连接光环形器7的第一端口，光环形器7的第二端口接入光纤光栅对阵列8、光环形器7的第三端口连接三分三耦合器13的左侧第一通信端、光环形器7的第四端口连接第一密集波分解复用器17的输入端，三分三耦合器13的左侧第二通信端连接第二密集波分解复用器18的输入端、三分三耦合器13的左侧第三通信端连接第三密集波分解复用器19的输入端、三分三耦合器13的右侧第一通信端通过延时光纤14连接第一法拉第旋转镜15、三分三耦合器13的右侧第二通信端打结悬空、三分三耦合器13的右侧第三通信端连接第二法拉第旋转镜16，第一密集波分解复用器17、第二密集波分解复用器18和第三密集波分解复用器19的输出端分别通过多通道光电探测器20连接多通道数据采集卡21的输入端。The high dynamic range dual-wavelength distributed optical fiber vibration demodulation system as shown in Figure 1 includes a first narrowband laser 1, a second narrowband laser 2, a dense wavelength division multiplexer 3, a pulsed light modulator 4, an erbium-doped laser Fiber amplifier 6, optical circulator 7, fiber grating pair array 8, three-point three-coupler 13 (3 × 3 coupler, enter from any port on the left, and three channels on the right can exit), the first Faraday rotating mirror 15, the third Two Faraday rotating mirrors 16, a first DWDM 17, a second DWDM 18, a third DWDM 19 and a multi-channel data acquisition card 21, wherein the first narrowband laser 1 and the laser signal output end of the second narrowband laser 2 are used to transmit two narrow linewidth laser signals with wavelengths of λ1 and λ2 to the two laser signal input ends of the dense wavelength division multiplexer 3 respectively. The dual-wavelength continuous light output end of 3 is connected to the signal input end of the pulsed light modulator 4, the dual-wavelength narrow light pulse output end of the pulsed light modulator 4 is connected to the input end of the erbium-doped fiber amplifier 6, and the output end of the erbium-doped fiber amplifier 6 Connect the first port of the optical circulator 7, the second port of the optical circulator 7 is connected to the fiber grating pair array 8, and the third port of the optical circulator 7 is connected to the left first communication end of the three-point three coupler 13, the optical ring The fourth port of the shaper 7 is connected to the input end of the first dense wave demultiplexer 17, and the second communication end on the left side of the three-point three-coupler 13 is connected to the input end of the second dense wave demultiplexer 18, the third The left third communication end of the triple coupler 13 is connected to the input end of the third dense wave demultiplexer 19 , and the right first communication end of the three-point triple coupler 13 is connected to the first Faraday rotating mirror 15 through the delay fiber 14 , the second communication terminal on the right side of the three-point three-coupler 13 is tied and suspended, the third communication terminal on the right side of the three-point three-coupler 13 is connected to the second Faraday rotating mirror 16, the first dense wave demultiplexer 17, the third The output ends of the second dense wave demultiplexer 18 and the third dense wave demultiplexer 19 are respectively connected to the input ends of the multi-channel data acquisition card 21 through the multi-channel photodetector 20 .
上述技术方案中，波长为λ1和λ2的两路窄线宽激光信号的传输和干涉都是独立的，因为它们对振动的敏感程度不同，因此利用这个可以准确解调振动信息。In the above technical solution, the transmission and interference of the two narrow linewidth laser signals with wavelengths λ1 and λ2 are independent, because they have different degrees of sensitivity to vibration, so the vibration information can be accurately demodulated by using this.
所述λ1为1535nm，所述λ2为1565nm，均处于掺铒光纤放大器6的工作波段边缘，以此获得抗躁性能更好的双波长下的相位信息，提高系统信噪比，对应的所述密集波分复用器3和密集波分解复用器17-19的两个通道的中心波长均分别是1535nm和1565nm；The λ 1 is 1535nm, and the λ 2 is 1565nm, which are both at the edge of the working band of the erbium-doped fiber amplifier 6, so as to obtain phase information under dual wavelengths with better anti-noise performance, improve the system signal-to-noise ratio, and the corresponding The center wavelengths of the two channels of the DWDM 3 and the DWDM 17-19 are respectively 1535nm and 1565nm;
上述技术方案中，它还包括双通道脉冲程序发生器5，双通道脉冲程序发生器5第一输出通道连接脉冲光调制器4的控制信号输入端，双通道脉冲程序发生器5第二输出通道连接多通道数据采集卡21的同步采集控制端，通过同步触发采集，来降低对脉冲程序发生器5的频率稳定性要求。In the above-mentioned technical scheme, it also includes a dual-channel pulse program generator 5, the first output channel of the dual-channel pulse program generator 5 is connected to the control signal input end of the pulsed light modulator 4, and the second output channel of the dual-channel pulse program generator 5 is connected. The synchronous acquisition control terminal of the multi-channel data acquisition card 21 is connected, and the frequency stability requirements for the pulse program generator 5 are reduced by synchronously triggering acquisition.
上述技术方案中，所述脉冲光调制器4用于将双波长连续光调制为双波长窄光脉冲，双波长窄光脉冲进入掺铒光纤放大器6后，输出放大了峰值功率的窄脉冲光信号，形成了分布式光栅阵列系统需要的稳定的放大窄脉冲光源，放大了峰值功率的窄脉冲光信号通过光环形器7，进入到光纤光栅对阵列8中。In the above technical solution, the pulsed light modulator 4 is used to modulate the dual-wavelength continuous light into dual-wavelength narrow light pulses, and after the dual-wavelength narrow light pulses enter the erbium-doped fiber amplifier 6, it outputs a narrow pulse light signal with amplified peak power. , forming a stable amplified narrow pulse light source required by the distributed grating array system, and the narrow pulse light signal with amplified peak power enters the fiber grating pair array 8 through the optical circulator 7 .
上述技术方案中，所述的光纤光栅对阵列8由多个光纤光栅对9和传感光纤12组成，提出的光纤光栅对是为了满足双波长光源以及光纤光栅分布式传感的需要，其中相邻两个光纤光栅对9之间通过传感光纤12连接，相邻两个光纤光栅对9之间的间距相等，所述光纤光栅对9由布拉格波长为λ1的光纤光栅10和布拉格波长为λ2的光纤光栅11相连组成。In the above technical solution, the fiber grating pair array 8 is composed of a plurality of fiber grating pairs 9 and sensing fibers 12. The proposed fiber grating pair is to meet the needs of dual-wavelength light sources and fiber grating distributed sensing. The two adjacent fiber grating pairs 9 are connected by a sensing fiber 12, and the spacing between the two adjacent fiber grating pairs 9 is equal. The fiber grating pair 9 is composed of a fiber grating 10 with a Bragg wavelength of The fiber gratings 11 of λ 2 are connected together.
上述技术方案中，掺铒光纤放大器6用于将窄脉冲激光的脉冲峰值功率进行放大，以此提高光栅阵列反射信号的信噪比。In the above technical solution, the erbium-doped fiber amplifier 6 is used to amplify the pulse peak power of the narrow pulse laser, so as to improve the signal-to-noise ratio of the reflected signal of the grating array.
上述技术方案中，所述第一密集波分解复用器17用于对三分三耦合器13输出的第一路干涉光进行波分解复用得到第一组波长为λ1和λ2的两路干涉光，第二密集波分解复用器18用于对三分三耦合器13输出的第二路干涉光进行波分解复用得到第二组波长为λ1和λ2的两路干涉光，第三密集波分解复用器19用于对三分三耦合器13输出的第三路干涉光进行波分解复用得到第三组波长为λ1和λ2的两路干涉光，每组波长为λ1和λ2的两路干涉光分别在多通道光电探测器20中进行光电转换后输送到多通道数据采集卡21中，通过波分解复用和多通道采集实现双波长独立干涉后相位信息的准确提取。In the above technical solution, the first dense wave demultiplexer 17 is used to perform wavelength demultiplexing and multiplexing on the first path of interference light output by the three-point three-coupler 13 to obtain a first group of two wavelengths with wavelengths λ 1 and λ 2 . The second dense wave demultiplexer 18 is used to demultiplex the second channel of interference light output by the three-point three-coupler 13 to obtain a second group of two channels of interference light with wavelengths λ 1 and λ 2 , the third dense wave demultiplexer 19 is used to demultiplex the third channel of interference light output by the three-point three-coupler 13 to obtain a third group of two channels of interference light with wavelengths λ 1 and λ 2 , each group The two channels of interference light with wavelengths of λ 1 and λ 2 are respectively photoelectrically converted in the multi-channel photodetector 20 and then sent to the multi-channel data acquisition card 21. After the dual-wavelength independent interference is realized through wave decomposition multiplexing and multi-channel acquisition Accurate extraction of phase information.
上述技术方案中，所述光纤光栅对阵列8的反射率范围为-40～-45dB，在该范围内的反射率具有良好的时分复用特性，可以达到较高的分布式光纤光栅复用容量，同时具有较低的光谱阴影和多重反射效应，满足振动需求的信噪比要求；In the above technical solution, the reflectivity of the fiber grating to the array 8 is in the range of -40 to -45dB, and the reflectivity within this range has good time division multiplexing characteristics, which can achieve a high distributed fiber grating multiplexing capacity. , while having lower spectral shadowing and multiple reflection effects, meeting the signal-to-noise ratio requirements of vibration requirements;
所述放大了峰值功率的窄脉冲光信号的脉冲宽度为10-45ns，峰值功率强度30dBm以上。考虑到光纤光栅对间隔5m，所以为了避免光脉冲同时覆盖两个光栅，而且减小瑞利散射带来的相位噪声，所以脉冲宽度和峰值功率强度需要经过计算确定。The pulse width of the narrow pulse optical signal with amplified peak power is 10-45ns, and the peak power intensity is above 30dBm. Considering that the fiber grating pair is separated by 5m, in order to avoid the optical pulse covering two gratings at the same time and reduce the phase noise caused by Rayleigh scattering, the pulse width and peak power intensity need to be determined by calculation.
上述技术方案中，所述三分三耦合器13、第一法拉第旋转镜15、第二法拉第旋转镜16和使干涉仪臂长差5m的延时光纤14构成非平衡迈克尔逊干涉仪，既满足了脉冲同步的问题，也同时消除了干涉中最难的偏振衰落问题。In the above technical solution, the three-point three-coupler 13, the first Faraday rotating mirror 15, the second Faraday rotating mirror 16, and the time-delay fiber 14 that makes the interferometer arm length difference 5m constitute an unbalanced Michelson interferometer, which not only satisfies the The problem of pulse synchronization is eliminated, and the most difficult problem of polarization fading in interference is also eliminated.
上述技术方案中，所述多通道数据采集卡21利用三分三耦合器数字解调算法和双波长回归分析算法对接收到的三组波长为λ1和λ2的两组干涉光强电信号进行相位解调和解缠，可以得到对应的分布式振动信息，实现了高动态范围下的分布式振动传感要求。In the above technical scheme, the multi-channel data acquisition card 21 utilizes a three-point three-coupler digital demodulation algorithm and a dual-wavelength regression analysis algorithm to receive three groups of wavelengths of λ 1 and λ 2 two groups of interference light intensity electrical signals By performing phase demodulation and unwrapping, the corresponding distributed vibration information can be obtained, and the distributed vibration sensing requirements under high dynamic range can be realized.
上述技术方案中，所述相邻两个光纤光栅对9之间的间距均为5m，为避免引入串扰，布拉格波长为λ1的光纤光栅10和布拉格波长为λ2的光纤光栅11之间的间距为2mm，布拉格波长为λ1(1535nm)的光纤光栅10和布拉格波长为λ2(1565nm)的光纤光栅11的栅区长度为2mm，故总的弱光纤光栅对空间长度为6mm，这个距离一方面考虑到光栅刻写带来的串扰问题，另一方面考虑到实际的光纤光栅对作为点式反射镜的要求。In the above technical solution, the distance between the two adjacent fiber grating pairs 9 is 5m. In order to avoid introducing crosstalk, the distance between the fiber grating 10 with the Bragg wavelength of λ 1 and the fiber grating 11 with the Bragg wavelength of λ 2 is 5m. The spacing is 2mm, the length of the grating region of the fiber grating 10 with the Bragg wavelength λ 1 (1535nm) and the fiber grating 11 with the Bragg wavelength λ 2 (1565nm) is 2mm, so the total space length of the weak fiber grating pair is 6mm, this distance On the one hand, the problem of crosstalk caused by grating writing is considered, and on the other hand, the requirements of the actual fiber grating as a point mirror are considered.
高动态范围的双波长分布式光纤振动解调系统工作时，被调制和放大的波长分别为1535nm和1565nm的窄线宽高功率脉冲通过四端口光环行器进入到光纤光栅对阵列中，通过光纤光栅对阵列反射的双波长脉冲光信号在3×3耦合器中发生干涉，并输出两个波长下的具有预设相位差的三路干涉光，在密集波分解复用器完成双波长激光的分离，并经过多通道光电探测器，得到六路干涉输出光强电信号I1，I2，I3，I4，I5，I6；When the dual-wavelength distributed optical fiber vibration demodulation system with high dynamic range works, the modulated and amplified narrow linewidth high-power pulses with wavelengths of 1535nm and 1565nm respectively enter the fiber grating pair array through the four-port optical circulator, and pass through the optical fiber. The double-wavelength pulsed optical signal reflected by the grating on the array interferes in a 3×3 coupler, and outputs three-way interference light with a preset phase difference at two wavelengths, and completes the dual-wavelength laser in the DWDM Separated, and passed through a multi-channel photodetector to obtain six channels of interference output light intensity electrical signals I 1 , I 2 , I 3 , I 4 , I 5 , I 6 ;
不同波长下，三分三耦合器的输出相位特性有明显差异，因此首先需要对三分三耦合器的输出相位特性进行参数估计，来实现对六路干涉信号的相位解调，得到分布式光纤振动解调系统同一振动信号在两个不同波长下引起的相位变化θ1w(n)和θ2w(n)，即本发明所述的相位解缠的初始相位；At different wavelengths, the output phase characteristics of the three-point three-coupler are significantly different. Therefore, it is necessary to first estimate the parameters of the output phase characteristics of the three-point three-coupler to realize the phase demodulation of the six-channel interference signal and obtain the distributed fiber vibration. The phase changes θ 1w (n) and θ 2w (n) caused by the same vibration signal of the demodulation system under two different wavelengths, that is, the initial phase of the phase unwrapping according to the present invention;
对上述初始相位进行回归分析，对发生缠绕的相位进行补偿，得到所述分布式光纤振动系统所测量的真实的相位值。Regression analysis is performed on the above initial phase, and the phase in which the winding occurs is compensated to obtain the real phase value measured by the distributed optical fiber vibration system.
利用双波长回归分析方法对接收到的所有干涉光强电信号进行相位解调得到对应的振动信息的具体过程如下：The specific process of performing phase demodulation on all received interference light intensity electrical signals to obtain the corresponding vibration information by using the dual-wavelength regression analysis method is as follows:
首先，同一振动信号在波长分别为λ1和λ2的激光下的数字相位变化分别为：First, the digital phase changes of the same vibration signal under lasers with wavelengths λ 1 and λ 2 are respectively:
其中，d(n)为信号臂和参考臂之间的光程差，θ1w(n)和θ2w(n)为同一振动信号在两个不同波长下引起的相位变化，θ1(n)和θ2(n)为同一振动信号在波长分别为λ1和λ2的激光下的数字相位变化，k1(n)和k2(n)分别表示n时刻下λ1和λ2两个波长的相位缠绕整数。where d(n) is the optical path difference between the signal arm and the reference arm, θ 1w (n) and θ 2w (n) are the phase changes caused by the same vibration signal at two different wavelengths, θ 1 (n) and θ 2 (n) are the digital phase changes of the same vibration signal under lasers with wavelengths λ 1 and λ 2 , respectively, k 1 (n) and k 2 (n) represent the two λ 1 and λ 2 at time n, respectively The phase wrapping integer for the wavelength.
将公式(1)(2)联立，可得：Combining formulas (1) and (2), we can get:
从上式中，我们可以得到k1(n)和k2(n)之间的关系式：From the above formula, we can get the relation between k 1 (n) and k 2 (n):
因为上式中k1(n)和k2(n)在实际的相位解缠中均为整数类型，于是定义回归误差e[k2(n)]：Since k 1 (n) and k 2 (n) in the above formula are both integer types in the actual phase unwrapping, the regression error e[k 2 (n)] is defined as:
e[k2(n)]＝{k1(n)-round[k1(n)]}2， (5)e[k 2 (n)]={k 1 (n)-round[k 1 (n)]} 2 , (5)
其中，round[k1(n)]表示k1(n)的四舍五入取整。where round[k 1 (n)] represents the rounding of k 1 (n).
对回归误差e[k2(n)]，在每个时刻，都可以获得最优的最小二乘解，即真实的相位解。同时，为了提高系统的解调速度，可以在k1(n-1)附近对k1(n)进行算法寻优，k1(n)和k1(n-1)分别表示第n时刻和第n-1时刻的k1值(相位缠绕系数)，这在一些静态解调或者微振动状态时解调效果更佳。For the regression error e[k 2 (n)], at each moment, the optimal least squares solution, that is, the real phase solution, can be obtained. At the same time, in order to improve the demodulation speed of the system, the algorithm can be optimized for k 1 (n) near k 1 (n-1), where k 1 (n) and k 1 (n-1) represent the nth time and The k 1 value (phase winding coefficient) at the n-1th time, which is better for demodulation in some static demodulation or micro-vibration states.
一种根据上述解调系统的高动态范围的双波长分布式光纤振动解调方法，其特征在于，它包括如下步骤：A dual-wavelength distributed optical fiber vibration demodulation method according to the high dynamic range of the above-mentioned demodulation system, it is characterized in that, it comprises the steps:
步骤1：第一窄带激光器1和第二窄带激光器2分别向密集波分复用器3输送波长为λ1和λ2的两路窄线宽激光信号，密集波分复用器3将波长为λ1和λ2的两路激光信号进行波分复用，输出双波长光信号；Step 1: The first narrowband laser 1 and the second narrowband laser 2 respectively transmit two narrow linewidth laser signals with wavelengths λ 1 and λ 2 to the dense wavelength division multiplexer 3, and the dense wavelength division multiplexer 3 converts the wavelength to The two laser signals of λ 1 and λ 2 are wavelength-division multiplexed to output dual-wavelength optical signals;
步骤2：脉冲光调制器4利用双通道脉冲程序发生器5第一输出通道产生的电脉冲，将双波长连续光调制为双波长窄光脉冲，随后进入掺铒光纤放大器6后，输出放大了峰值功率的窄脉冲光信号；Step 2: The pulse light modulator 4 modulates the two-wavelength continuous light into two-wavelength narrow light pulses by using the electrical pulses generated by the first output channel of the two-channel pulse program generator 5, and then enters the erbium-doped fiber amplifier 6, and the output is amplified. narrow pulse optical signal with peak power;
步骤3：放大了峰值功率的窄脉冲光信号从光环形器7的第一端口接入，从光环形器7的第二端口输出到光纤光栅对阵列8中，光纤光栅对阵列8中的每个光纤光栅对9形成一个反射面，用于反射双波长光脉冲，在光纤光栅对阵列8中，前一个光纤光栅对9反射的双波长窄光脉冲与后一个光纤光栅对9反射的双波长窄光脉冲在时间上刚好重合，从而在由三分三耦合器13、第一法拉第旋转镜15、第二法拉第旋转镜16和延时光纤14构成的非平衡迈克尔逊干涉仪中形成双波长干涉信号，并且两个波长的激光之间各自进行干涉、互不影响，三分三耦合器13再将双波长干涉光进行分光处理，输出具有预设相位差的三路干涉光；Step 3: The narrow pulse optical signal with amplified peak power is connected from the first port of the optical circulator 7, and output from the second port of the optical circulator 7 to the fiber grating pair array 8, and each fiber grating pair array 8 The fiber grating pairs 9 form a reflective surface for reflecting dual-wavelength light pulses. In the fiber grating pair array 8, the dual-wavelength narrow light pulses reflected by the former fiber grating pair 9 and the dual-wavelength light pulses reflected by the latter fiber grating pair 9 The narrow light pulses just coincide in time to form a two-wavelength interference in the unbalanced Michelson interferometer composed of the three-point three-coupler 13 , the first Faraday rotating mirror 15 , the second Faraday rotating mirror 16 and the time delay fiber 14 signal, and the two wavelengths of laser light interfere with each other without affecting each other, and the three-point three-coupler 13 then splits the two-wavelength interference light to output three-way interference light with a preset phase difference;
步骤4：所述第一密集波分解复用器17用于对三分三耦合器13输出的第一路干涉光进行波分解复用得到第一组波长为λ1和λ2的两路干涉光，第二密集波分解复用器18用于对三分三耦合器13输出的第二路干涉光进行波分解复用得到第二组波长为λ1和λ2的两路干涉光，第三密集波分解复用器19用于对三分三耦合器13输出的第三路干涉光进行波分解复用得到第三组波长为λ1和λ2的两路干涉光，三组波长为λ1和λ2的两路干涉光分别在多通道光电探测器20中进行光电转换后输送到多通道数据采集卡21中；Step 4: The first dense wave demultiplexer 17 is used to perform wavelength demultiplexing and multiplexing on the first interference light output by the three-to-three coupler 13 to obtain a first group of two interference lights with wavelengths λ 1 and λ 2 light, the second dense wave demultiplexer 18 is used to demultiplex the second path of interference light output by the three-to-three coupler 13 to obtain a second group of two paths of interference light with wavelengths λ 1 and λ 2 , The three-dense wave demultiplexer 19 is used for demultiplexing and multiplexing the third path of interference light output by the three-point three-coupler 13 to obtain a third group of two paths of interference light with wavelengths λ 1 and λ 2 , and the three groups of wavelengths are The two paths of interference light of λ 1 and λ 2 are respectively photoelectrically converted in the multi-channel photodetector 20 and then sent to the multi-channel data acquisition card 21;
步骤5：所述多通道数据采集卡21利用三分三耦合器数字解调算法和双波长回归分析算法对接收到的三组波长为λ1和λ2的两路干涉光强电信号进行相位解调和解缠，得到对应的分布式振动信息，具体方法见专利号为201910091369.0的中国专利《基于双波长回归分析的光纤振动传感器相位解调装置与方法》。Step 5: The multi-channel data acquisition card 21 uses the three-point three-coupler digital demodulation algorithm and the dual-wavelength regression analysis algorithm to phase the received three groups of two-channel interference light intensity electrical signals with wavelengths λ 1 and λ 2 . The corresponding distributed vibration information is obtained by demodulation and unwrapping. For the specific method, see the Chinese patent "Phase Demodulation Device and Method of Optical Fiber Vibration Sensor Based on Dual-Wavelength Regression Analysis" with patent number 201910091369.0.
本发明解决现有的分布式光纤振动解系统中相位解调技术动态测量范围受限以及对数据采集系统采样率要求过高的问题，提供一种更加灵活的不受传统的π相位原则限制的解调系统与方法，实现低采样率下的大量程分布式光纤振动传感信号解调，使之能够适用于铁轨振动监测、光纤水听器、周界安防等存在分布式大幅度振动信号测量需求的应用领域。The invention solves the problems that the dynamic measurement range of the phase demodulation technology in the existing distributed optical fiber vibration solution system is limited and the sampling rate of the data acquisition system is too high, and provides a more flexible solution that is not limited by the traditional π phase principle. The demodulation system and method can realize the demodulation of large-range distributed optical fiber vibration sensing signal at low sampling rate, so that it can be applied to the measurement of distributed large-scale vibration signal such as railway vibration monitoring, optical fiber hydrophone, and perimeter security. required application areas.
本说明书未作详细描述的内容属于本领域专业技术人员公知的现有技术。The content not described in detail in this specification belongs to the prior art known to those skilled in the art.
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